<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>选择器和盒子模型</title>
    <link rel="stylesheet" href="盒子.css">
</head>
<body>
    <div class="demo">
        <img src="盒子模型图.png" alt="图片无法显示">
    </div>
</body>
</html>